Fuel management system and method

ABSTRACT

A fuel management system and method that permits accurate accounting of fuel consumption within the context of a fuel consuming system is disclosed. The system/method may be broadly described as comprising a fuel level sensor, fuel level sensor transponder, fuel accounting system, and optional regulated fuel dispenser. The fuel level sensor accurately determines the contents of a fuel tank. This information is reported via fuel sensor transponder to a fuel accounting system that tracks the fuel consumption of the fuel consuming system and provides billing information based on the detected fuel consumption. This accounting information may be utilized within an optional regulated fuel dispenser to refill the fuel tank to an accurately predetermined fuel level for the next fuel management accounting cycle. While the present invention has many applications, one preferred embodiment targets fuel management within the context of rental/lease vehicles and the like.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable

PARTIAL WAIVER OF COPYRIGHT

All of the material in this patent application is subject to copyrightprotection under the copyright laws of the United States and of othercountries. As of the first effective filing date of the presentapplication, this material is protected as unpublished material.

However, permission to copy this material is hereby granted to theextent that the copyright owner has no objection to the facsimilereproduction by anyone of the patent documentation or patent disclosure,as it appears in the United States Patent and Trademark Office patentfile or records, but otherwise reserves all copyright rights whatsoever.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

FIELD OF THE INVENTION

The present invention generally relates to systems and methods formanaging fuel consumption and accounting for same within the context ofsupporting the needs of one or more fuel consuming systems. This fieldincludes but is not limited generally to situations in which fuelconsumption is managed and accounted for within a fleet of motorvehicles, automobiles, and/or trucks.

PRIOR ART AND BACKGROUND OF THE INVENTION

A common issue regarding the rental/lease of automobiles, trucks, motorvehicles, and other fuel consuming systems is the management andaccounting for fuel use within these fuel consuming systems and properchargeback to the rental/lease customer for situations in which fuel isconsumed but not replaced by the customer. Typical approaches to thisfuel accounting methodology require that the rental/lease agency issuethe motor vehicle with a “full” fuel tank and require that the customerreturn the motor vehicle with a “full” fuel tank. If the customerreturns the vehicle with a fuel gauge indicating anything less than a“full” tank, the rental/lease agency generally refills the fuel tank toa “full” level and charges the rental/lease customer appropriate feesbased on the vehicle rental/lease contract.

While minor discrepancies in fuel tank contents may seem insignificantin the overall profitability in the rental/lease vehicle market, itshould be noted that the rental car market in the United States hasannual revenue of approximately USD$21 billion, with a fleet ofapproximately 1.6 million automobile rental vehicles (2010 data). Thisrental fleet services at least 22 million auto rental transactions peryear (VISA® brand credit card rental car transaction count for 2004).This data would on its face suggest each transaction accounted forapproximately USD$1000.00. However, a more realistic transaction countwould be approximately one-quarter of this value, or approximatelyUSD$250.00 (given that the transaction count cited was for a specificcredit card vendor). This analysis could easily yield 50+ million autorental transactions per year. If each of these rentals is associatedwith a half gallon of unrecovered fuel cost, the total lost profit forthis market could easily reach USD$100 million per year, or 0.5% ofoverall revenue, a significant profit loss given the overall profitmargins in the industry.

Various fuel accounting issues are associated with this conventionalprior art approach and include but are not limited to the following:

-   -   What constitutes a “full” fuel tank is extremely subjective, as        the fuel gauges in most motor vehicles are generally nonlinear        and subject to significant inaccuracies.    -   Customers may return the vehicle with less fuel than was        originally in the fuel tank when the vehicle was issued to them,        but due to inaccuracies in the fuel gauges of most vehicles this        discrepancy may not be noticed, accounted for, or charged to the        customer.    -   Refilling of fuel tanks by various rental/lease employees may        result in inconsistent amounts of fuel in the fuel tank as the        vehicle is issued to the rental/lease customer.    -   The definition of a “full” tank, as both defined by the vehicle        rental/lease agency and the customer may have different meanings        because neither party has an accurate method of determining fuel        tank contents.    -   Since neither the rental/lease agency nor customer can determine        the exact fuel tank contents, neither party has sufficient        information as to how much fuel should be added to the fuel tank        to constitute a “full” tank of fuel.    -   In many circumstances the vehicle rental/lease agency loses        revenue on returned vehicles that contain less fuel than when        the vehicles were issued, but the resolution of prior art fuel        gauges do not permit the level of fuel tank level accuracy to        properly account for these losses. As a result, vehicle        rental/lease agencies may lose millions of dollars annually due        to these unrecoverable fuel losses.

The inability of vehicle rental/lease agencies to accurately managetheir fuel costs can result in significant lost profits, as the fueltank refilling charges account for a significant profits stream forthese companies. However, to date no accurate methodology has beenproposed to manage fuel recovery costs for these companies or to provideany methodology of defining a “full” fuel tank in these situations.

DEFICIENCIES IN THE PRIOR ART

The prior art as detailed above suffers from the following deficiencies:

-   -   Current methodologies of determining the contents of a fuel tank        are generally too inaccurate to provide suitable fuel accounting        management.    -   Traditional fuel sensors within fuel tanks are not suitable for        accurate measurement of fuel tank contents.    -   Traditional methods of fuel tank filling by rental/lease        agencies are prone to discrepancies in the amount of fuel placed        in the tank based on a number of factors, including operator        variances, fuel pump characteristics, time of day, temperature,        etc.    -   Consumers of rental/lease automobiles, trucks, and the like have        no reliable methodology to determine when the fuel tank is        “full”.    -   Automobile, truck, and other rental/lease agencies have no        accurate methodology to determine if a fuel tank is “full” and        lack any standardization as to how a “full” tank of fuel is to        be defined.    -   As environmental temperature may vary significantly in vehicle        rental/lease environments, the fuel tank volume may vary        significantly based on these environmental factors, and to date        there is no methodology to compensate for this effect.    -   In a rental/lease vehicle context, many customers return the        rental/lease vehicle with “overfull” fuel tank levels that may        spill or waste fuel when the vehicle is rented/leased to the        next customer. No provision is made in the prior art to mitigate        or reduce the environmental hazards associated with this        practice.    -   In a rental/lease vehicle context, the refueling of rental/lease        vehicles may incur significant variances based on the fueling        operator, fuel pump used, and other environmental factors. As        such, some refueled rental/lease vehicles may leave the        rental/lease facility with “overfull” fuel tank levels that may        spill or waste fuel when the vehicle is used by the current        rental/leasing customer. No provision is made in the prior art        to mitigate or reduce the environmental hazards associated with        this practice.

While some of the prior art may teach some solutions to several of theseproblems, the core issue of fuel management, especially in the contextof a rental/lease environment has not been addressed.

OBJECTIVES OF THE INVENTION

Accordingly, the objectives of the present invention are (among others)to circumvent the deficiencies in the prior art and affect the followingobjectives:

-   -   (1) Provide for a fuel management system and method that permits        accurate determination of fuel tank contents.    -   (2) Provide for a fuel management system and method that permits        accurate calibration of fuel tank fuel level sensors.    -   (3) Provide for a fuel management system and method that permits        individual calibration of fuel tank fuel level sensors to their        associated fuel tank.    -   (4) Provide for a fuel management system and method that permits        a rental/lease agency to accurately define a “full” tank of fuel        within a fuel tank.    -   (5) Provide for a fuel management system and method that permits        a retail consumer of rental/lease automobile/truck the ability        to determine if the fuel tank is “full”.    -   (6) Provide for a fuel management system and method that permits        a retail agency to accurately “fill” a fuel tank to a        predetermined accurate “full” level.    -   (7) Provide for a fuel management system and method that permits        returned automobile/truck rentals to be accurately charged for        fuel tanks that are not returned “full”.    -   (8) Provide for a fuel management system and method that permits        quick determination as to whether a fuel tank is “full”.    -   (9) Provide for a fuel management system and method that permits        “overfull” fuel tanks to be normalized to a predetermined “full”        level.    -   (10) Provide for a fuel management system and method that        reduces the environmental damage caused by “overfull” fuel        tanks.    -   (11) Provide for a fuel management system and method that        permits fuel recovery from fuel tanks that have been        “overfilled”.

While these objectives should not be understood to limit the teachingsof the present invention, in general these objectives are achieved inpart or in whole by the disclosed invention that is discussed in thefollowing sections. One skilled in the art will no doubt be able toselect aspects of the present invention as disclosed to affect anycombination of the objectives described above.

BRIEF SUMMARY OF THE INVENTION System Overview

The present invention and typical system application as applied to afuel management system may take many forms, but a preferred exemplaryembodiment as illustrated within the context of a rental/leaseautomobile/truck environment is indicative of the breadth of theinvention. The system/method may be broadly described as comprising afuel level sensor, fuel level sensor transponder, fuel accountingsystem, and optional regulated fuel dispenser. The fuel level sensoraccurately determines the contents of a fuel tank. This information isreported (typically wirelessly) via fuel sensor transponder to a fuelaccounting system that tracks the fuel consumption of the fuel consumingsystem and provides billing information based on the detected fuelconsumption. This fuel accounting information may be utilized within anoptional regulated fuel dispenser to refill the fuel tank to anaccurately predetermined fuel level for the next fuel managementaccounting cycle.

The system may incorporate a variety of fuel level sensors, but apreferred exemplary embodiment utilizes an ultrasonic fuel level sensorembodied in a fuel tank cap or other fuel tank covering that permits thefuel tank level to be accurately determined with no physical contact tothe fuel within the fuel tank. The fuel tank sensor transponderoptimally operates in a wireless fashion to transmit informationdescribing the fuel tank level to a computer system running fuel tankaccounting software. This accounting software may log the fuel tanklevel as the automobile/truck is rented/leased and then again when theautomobile/truck is returned. Differentials in measured fuel tankcontents may be automatically billed to the rental/lease consumer basedon the contracted fuel reimbursement costs.

The measured fuel tank level upon return of the rental/lease vehicle maybe input into a fuel dispenser that automatically dispenses fuel to thefuel tank in an amount sufficient to restore the fuel tank to apredetermined “full” level. By coordinating the fuel dispenser to theknown fuel tank contents, the fuel tank may be refilled to an accuratelyknown “full” level after each vehicle return, thus eliminating thepossibility of overfilling or wasting fuel in the refilling process.

Method Overview

The present invention method can be generally described as incorporatingthe following steps:

-   -   Accurately sensing the level of fuel in a fuel tank;    -   Transmitting this fuel level information via a fuel level sensor        transponder;    -   Receiving the fuel level information in a fuel accounting        system;    -   Tracking the fuel level information associated with a given        customer in a customer database;    -   Optionally refilling the fuel tank using a fuel dispenser system        that is controlled by the fuel accounting system based on the        difference between the measured fuel tank level and a        predetermined “full” fuel tank level.

This general method may be modified heavily depending on a number offactors, with rearrangement and/or addition/deletion of stepsanticipated by the scope of the present invention. Integration of thisand other preferred exemplary embodiment methods in conjunction with avariety of preferred exemplary embodiment systems described herein isanticipated by the overall scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the advantages provided by the invention,reference should be made to the following detailed description togetherwith the accompanying drawings wherein:

FIG. 1 illustrates a generalized system overview of a preferredexemplary embodiment of the present invention;

FIG. 2 illustrates a generalized method flowchart of a preferredexemplary embodiment of the present invention;

FIG. 3 illustrates a generalized system overview of a preferredexemplary embodiment of an ultrasonic fuel level sensor system useful insome preferred embodiments of the present invention;

FIG. 4 illustrates a generalized method overview of a preferredexemplary embodiment of an ultrasonic fuel level sensor method useful insome preferred embodiments of the present invention;

FIG. 5 illustrates a generalized system overview of a preferredexemplary embodiment of an ultrasonic fuel level sensor calibrationsystem useful in some preferred embodiments of the present invention;

FIG. 6 illustrates a generalized method overview of a preferredexemplary embodiment of an ultrasonic fuel level sensor calibrationmethod useful in some preferred embodiments of the present invention;

FIG. 7 illustrates a generalized system overview of preferred exemplaryembodiment of the present invention as applied to a rental/lease fuelmanagement system;

FIG. 8 illustrates a generalized method overview of preferred exemplaryembodiment of the present invention as applied to a rental/lease fuelmanagement method;

FIG. 9 illustrates a generalized method overview of a fuel tank fuelmanagement method useful in some preferred embodiments of the presentinvention;

FIG. 10 illustrates a system block diagram of a preferred exemplaryembodiment of an ultrasonic fuel level sensor system useful in somepreferred embodiments of the present invention;

FIG. 11 illustrates a preferred exemplary embodiment of the presentinvention utilizing a modified fuel tank sensor tube and float ball toenhance fuel tank fuel level sensing in some preferred embodiments ofthe present invention;

FIG. 12 illustrates a preferred exemplary embodiment of the presentinvention utilizing an existing inline fuel tank fuel gauge sensor asthe fuel level sensing element for some preferred embodiments of thepresent invention;

FIG. 13 illustrates a generalized method overview of a preferredexemplary embodiment of an inline fuel level sensor calibration methoduseful in some preferred embodiments of the present invention;

FIG. 14 illustrates an exemplary system block diagram of a low/zeropower communications system useful in some preferred exemplaryembodiments of the present invention;

FIG. 15 illustrates exemplary power receiver configuration switchingstates and their associated circuitry associated with some preferredexemplary embodiments of a low/zero power communications system usefulin some preferred exemplary embodiments of the present invention;

FIG. 16 illustrates an exemplary method flowchart useful in implementingsome preferred exemplary embodiments of the present inventionincorporating fuel dispensing compensation for thermal fuel expansioncoefficients.

DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetailed preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiment illustrated.

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment, wherein these innovative teachings are advantageouslyapplied to the particular problems of a FUEL MANAGEMENT SYSTEM ANDMETHOD. However, it should be understood that this embodiment is onlyone example of the many advantageous uses of the innovative teachingsherein. In general, statements made in the specification of the presentapplication do not necessarily limit any of the various claimedinventions. Moreover, some statements may apply to some inventivefeatures but not to others.

Fuel Level Sensor Not Limitive

The present invention has as one of its features the accurate detectionof fuel level within a fuel tank system. While the present inventiondoes not limit the technology used to achieve this functionality, manypreferred exemplary embodiments utilize an ultrasonic transducer toexcite the unfilled cavity within the fuel tank to determine the amountof fuel present within the fuel tank. While this is viewed as theoptimal methodology to achieve this desired function, the presentinvention does not limit the scope of the invention to this particularmethod of fuel level determination.

“Fuel Cap” Fuel Level Sensor Not Limitive

The present invention in some preferred exemplary embodiments utilizes afuel level sensor integrated into the fuel cap (“gas cap”) used to coverthe fuel filling point of the fuel tank. This particular methodology ofintegrating the fuel level sensor into the overall system is believed tobe optimal, but the present invention is not limited to this particularembodiment in implementing the fuel level sensor functionality.

Fuel Type Not Limitive

The present invention may be applied to a wide variety of fuel types,including but not limited to petroleum based fuels such as gasolineand/or diesel. However, the teachings of the present invention are notlimited to any particular fuel type, and may include other forms ofstored energy, including but not limited to compressed gasses, etc. Insummary, the particular fuel associated with the fuel consuming systemis ancillary to the methodologies detailed herein used to manage thefuel used within the fuel consuming system.

Fuel Consuming System Not Limitive

The present invention in some preferred embodiments may be applied to awide variety of fuel consuming systems, such as automobiles, busses,trucks, motorcycles, boats, personal water craft, planes, snowmobiles,lawnmowers (and related farm/garden systems, generators, etc. However,the particular type of fuel consuming system is not limited by the scopeof the present invention. Therefore, the term “fuel consuming system”should be given its broadest possible interpretation in this context.

“Full” Fuel Tank Not Limitive

The present invention in many preferred exemplary embodiments attemptsto standardize the amount of fuel within a fuel tank within the contextof a fuel consuming system. Within this context, a standardized “full”fuel tank level is optimally the target of the system. However, theexact definition of what constitutes “full” may vary widely based on thespecific application of the invention system/method.

For example, within some contexts it will be sufficient to fill the fueltank with a known quantity of fuel that may or may not be the absoluteor even rated capacity of the fuel tank. Some circumstances may dictatelimiting the fuel within the fuel tank to enhance overall fuel economyby reducing overall vehicle weight. In many cases the absolute value ofa “full” tank is not as important as the fact that the same fuel levelis consistently placed within the fuel tank in a given context.Therefore, the term “full” should be given its broadest possibleinterpretation within the context of the present invention disclosure,with an emphasis being placed on situations where the meaning of “full”is defined and standardized within the context of the application.

Rental/Lease Vehicle Not Limitive

The present invention in some preferred embodiments may be applied tosituations in which fuel a rental/lease vehicle is accounted for and/ordispensed by a fuel management system/method as detailed herein. Howeverthe particular type of rental/lease vehicle is not limited by the scopeof the present invention. Therefore, the term “rental vehicle” “leasevehicle” or “rental/lease vehicle” should be broadly interpreted toinclude any “fuel consuming system” that is the subject of a rentaland/or lease agreement.

Transponder Not Limitive

The present invention in some preferred embodiments may utilize atransponder to transmit fuel level sensor information to a fuelaccounting system. The present invention makes no limitation on the formof this transponder, and it may take the form of a magnetic,radio-frequency, RFID, and/or other form of wireless transmission withno loss of generality in the overall invention scope. However, thepresent invention does specifically anticipate (and incorporates hereinby reference) the utilization of the wireless technologies detailed inU.S. Pat. No. 5,025,486 (now expired) for WIRELESS COMMUNICATION SYSTEMWITH PARALLEL POLLING, issued on Jun. 18, 1991, to Kevin M. Klughart.This patent disclosure discloses both the use of 200 Khz and 300 Mhz lowpower transponder communication mechanisms. While this technology may beapplicable to some embodiments of the present invention, otherembodiments may use different transponder communication methodologies.

Identification and Security

The present invention may incorporate layers of identification andsecurity within the context of the fuel level sensor and associatedelectronics to (among other things) verify the integrity of the fuellevel sensor calibration data, prevent fraud, protect sensitive customerinformation, and in some cases streamline the processing of data fromthe fuel level sensor. While there are many methodologies to uniquelyidentify the fuel level sensor, one preferred methodology uses the MaximIntegrated Products, Inc. model DS2401 Silicon Serial Number integratedcircuit as the identifying agent. In addition, the use of MaximIntegrated Products, Inc. 1-WIRE® brand memory products may be used tostore calibration data, vehicle VIN information, customer information,etc. within the context of many preferred embodiments of the presentinvention.

General Invention System Architecture (0100)

The general system architecture of the present invention is generallyillustrated in FIG. 1 (0100). In this exemplary architecture the systemis illustrated as applied to servicing a fuel consuming system (0110)herein depicted as an automobile. This fuel consuming system (0110) isgenerally equipped with a fuel tank (0111) that may take a variety offorms. The present invention generally comprises a fuel level sensor(0101) that detects the amount of fuel present within the fuel tank(0111). This fuel level sensor (0101) communicates with a fuel levelsensor transponder (0102) that converts the fuel level information to awireless data stream (0107) that is relayed to a fuel accounting system(0103) running on a computer system under control of computer softwareretrieved from computer readable media (0105). A computer readablecustomer database (0106) maintains information on specific customers,their relationship to particular fuel consuming systems (0110), andinformation on fuel consumption retrieved from the fuel level sensor(0101) via the fuel level sensor transponder (0102). Some preferredexemplary embodiments implement a fuel dispenser system (0104) thatdetermines how much fuel is required to “fill” the fuel tank (0111) byretrieving fuel tank (0111) level information from the fuel sensor(0101) and/or fuel accounting system (0103) and then replacing thisexact amount of fuel in the fuel tank (0111).

General Invention Method Architecture (0200)

The general method architecture of the present invention is generallyillustrated in FIG. 2 (0200). In this exemplary architecture the methodis illustrated as applied to servicing a fuel consuming system. Themethod steps generally comprise the following:

-   -   Accurately sensing the level of fuel in a fuel tank (0201);    -   Transmitting this fuel level information via a fuel level sensor        transponder (0202);    -   Receiving the fuel level information in a fuel accounting system        (0203);    -   Tracking the fuel level information associated with a given        customer or vehicle in a customer database (0204);    -   Determining if fuel tank refilling is enabled, and if not,        proceeding to step (8) (0205);    -   Subtracting the measured fuel level from a “full” tank value to        determine the fuel tank “refill” quantity (0206);    -   Refilling the fuel tank using a fuel dispenser system that is        controlled by the fuel accounting system based on the difference        between the measured fuel tank level and a predetermined “full”        fuel tank level (0207);    -   Terminating the fuel accounting cycle (0208).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

This fuel management method has several advantages over the prior art.Specifically, the accurate measurement of fuel tank contents permitsaccurate accounting as to the amount of fuel that the customer must payfor and which is below the predetermined “full” fuel tank level.Additionally, if an automated fuel dispenser is utilized as in steps (6)and (7), only the required amount of fuel necessary to reach thepredetermined “full” fuel tank level is added to the tank to completethe refill operation.

This is in contrast to traditional refueling operations in whichemployees manually determine when the fuel tank is full (typically via afuel pump dispenser shutoff trigger). This methodology can beuntrustworthy, as it may depend on variables such as fuel flow rates,operator inconsistencies, and other factors that cannot be easilystandardized.

Fuel Level Sensor System (0300)

One key element of the present is the use of a fuel level sensor thatpermits accurate determination of the fuel level within a fuel tank.Instead of utilizing the conventional fuel level sensors typicallyinstalled on fuel tanks, the present invention opts in some preferredembodiments for an alternate system that permits much more accuratedetermination of the exact amount of fuel within a fuel tank.

To accomplish this feature, the present invention utilizes in manypreferred embodiments an ultrasonic fuel level sensor system. Thissystem in its best mode embodiment utilizes a modified fuel tank fillingcap (“gas cap”) that incorporates an ultrasonic source and detector thatpermit accurate determination of the fuel level within the fuel tank.

Referencing FIG. 3 (0300), the general fuel level sensor utilizes anultrasonic source (0301) to flood the fuel tank (0310) with ultrasonicenergy with a fixed and determinate wavefront (0302). Depending on thefuel level (0311, 0312) in the tank, the return time associated with theechoed ultrasonic energy (0304) will vary, sometimes in a nonlinearfashion. An ultrasonic detector (0303) captures this return delay timeto determine the fuel level (0313, 0314) currently present in the fueltank (0310).

Fuel Level Sensor Method (0400)

The fuel level sensor system described above has an associated methodarchitecture as generally illustrated in FIG. 4 (0400). The method stepsgenerally comprise the following:

-   -   Activating an ultrasonic source to send an ultrasonic energy        wave into the fuel tank fill point (0401);    -   Waiting for a returned ultrasonic echo, as the ultrasonic energy        wave impinges the surface of the fuel within the fuel tank and        is reflected back to the fuel tank fill point (0402);    -   Measuring the ultrasonic return echo time (0403);    -   Interpolating the return echo time within data contained within        a fuel tank calibration table (0404);    -   Calculating the current fuel tank level using fuel tank level        data (0410) from a prior fuel tank calibration (0405).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

It should be noted that the fuel tank level data (0410) obtained from aprior fuel tank calibration procedure generally includes paired datapoints including a known fuel tank level and the corresponding returnecho time. Given the nonlinear nature of the ultrasonic echo waveforms,this table may be highly nonlinear and in some circumstances require theuse of ultrasonic harmonics (added as a third vector in the calibrationtable) to accurately determine the fuel level within the fuel tank. Thecalculation of an accurate fuel tank level may require the use of anonlinear fitting function to be applied to the calibration data (0410),and thus step (5) may require application of a nonlinear interpolationfunction. Nonlinear interpolation utilizing calibration datasets such asthose illustrated in FIG. 4 (0410) are well known to those skilled inthe mathematical arts.

Fuel Level Sensor Calibration System (0500)

The present invention in some preferred exemplary embodiments mayincorporate an automated fuel level sensor calibration system asgenerally depicted in FIG. 5 (0500). Since one goal of some embodimentsof the invention is to provide accurate determination of fuel tankcontents, some preferred embodiments utilize ultrasonic sensing of thefuel tank contents. Since the fuel tanks on which the invention may beused may vary considerably, the use of a fuel filler cap sensor for fueltank level sensing is not a solution that can be generally applied to awide variety of fuel tanks, unless some methodology is provided toindividually calibrate the fuel level sensor to a given fuel tank. Thesystem generally illustrated in FIG. 5 (0500) provides for thisfunctionality.

The system (0500) generally comprises a computer system (0501) runningsoftware read from computer readable medium (0502) that communicateswirelessly (0503) to a fuel tank filler cap embodiment (0504) of a fuelsensor having a resealable hole (0505) into which a fuel dispensing hosecan be placed. The fuel tank filler cap embodiment of the fuel sensor(0506) is preferably an ultrasonic sensor type as previously discussed.The fuel dispenser (0508) is preferably automated in this context, inthat it receives commands from the fuel tank filler cap embodiment(0504) to dispense a known amount of fuel into the fuel tank (0507),after which the fuel tank sensor (0506) detects the fuel tank levelbased on the ultrasonic return echo time. This echo time is then loadedinto a fuel tank calibration table (0521) that may be associated with afuel tank database (0522). This information may be utilized by the fueltank ultrasonic sensor (0506) and/or the computer system (0501) tocalibrate the fuel tank sensor ultrasonic echo times to known fuel tanklevels.

Several variants of this preferred embodiment are possible, includingscenarios wherein the computer system drives the transfer of fuel fromthe fuel dispenser (0508) to the fuel tank (0507). Fuel sensorcalibration data can be used by the computer system to determine fueltank levels, or this information can be incorporated into the fuel tanksensor itself to report actual fuel tank contents rather than simplyrecording ultrasonic return echo times. In some sophisticatedembodiments the raw data associated with the ultrasonic return echo maybe reported back to the computer system (0501) for analysis and accuratedetermination of the fuel tank contents. Multiple ultrasonicfrequencies, some including harmonics, may be utilized to provide a moreaccurate indicator of fuel tank contents in some circumstances.

Fuel Level Sensor Calibration Method (0600)

The fuel level sensor calibration system described above has anassociated method architecture as generally illustrated in FIG. 6(0600). The method steps generally comprise the following:

-   -   Draining the fuel tank to a known level (0601);    -   Initializing the fuel level sensor calibration state to indicate        that the sensor is being calibrated to the fuel tank (0602);    -   Triggering a fuel dispenser to transfer a known quantity of fuel        into the fuel tank (0603);    -   Ultrasonically probing the fuel tank cavity to record the return        echo time and/or return echo characteristics associated with the        current fuel level within the fuel tank (0604);    -   Recording the return echo time and/or return echo        characteristics and fuel tank level in a fuel tank calibration        database table (0610) for use later in determining the fuel        level within the fuel tank (0605);    -   Determining if the fuel tank fill level has been reached, and if        not, proceeding to step (3) (0605).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

It should be noted that the fuel tank level data (0610) generated bythis fuel tank calibration procedure generally includes paired datapoints including a known fuel tank level and the corresponding returnecho time. Given the nonlinear nature of the ultrasonic echo waveforms,this table may be highly nonlinear and in some circumstances require theuse of ultrasonic harmonics (added as a third vector in the calibrationtable) to accurately determine the fuel level within the fuel tank. Thecalculation of an accurate fuel tank level may require the use of anonlinear fitting function to be applied to the calibration data (0610).Nonlinear interpolation utilizing calibration datasets such as thoseillustrated in FIG. 6 (0610) are well known to those skilled in themathematical arts.

Rental/Lease Fuel Management System (0700)

The present invention in some preferred exemplary embodiments may beadvantageously applied to rental/lease fuel management system asgenerally illustrated in FIG. 7 (0700). While this system is primarilytargeted towards rental/lease vehicle fuel management, the system can beapplied to any situation in which a fuel consuming system is integratedwith a fuel management system.

This particular preferred embodiment of the present invention isparticularly well suited to situations in which rental/lease vehiclesand the fuel that they consume are managed by an overall fuel managementsystem. Of particular importance in these situations is the eliminationof fuel waste at all points in the rental/lease management cycle. Onemethodology of fuel conservation is to prevent “overfilling” of the fueltank, both at the rental/lease dispatch point and when the rental/leasevehicle is returned by the customer. This preferred exemplary embodimentachieves this goal by ensuring that the rental/lease vehicle isdispatched with a “full” tank of fuel and is returned to inventory witha “full” tank of fuel. The definition of a “full” tank of fuel may notbe the absolute fuel tank capacity, but may be some other value thatensures minimal waste of fuel due to tank overfilling, spillage, etc.

This preferred exemplary system embodiment (0700) generally comprises acomputer system (0701) running software read from computer readablemedium (0702) that communicates wirelessly (0703) to a fuel tank fillercap embodiment (0704) of a fuel sensor having a resealable hole (0705)into which a fuel dispensing hose (0708) can be placed. The fuel tankfiller cap embodiment of the fuel sensor (0706) is preferably anultrasonic sensor type as previously discussed. The fuel dispenser(0708) is preferably automated in this context, in that it receivescommands from the fuel tank filler cap embodiment (0704) to dispense aknown amount of fuel into the fuel tank (0707), after which the fueltank sensor (0706) detects the fuel tank level based on the ultrasonicreturn echo time. This echo time is then loaded into a fuel tankcalibration table (0721) that may be associated with a fuel tankdatabase (0722). This information may be utilized by the fuel tankultrasonic sensor (0706) and/or the computer system (0701) to calibratethe fuel tank sensor ultrasonic echo times to known fuel tank levels.

Integrated into this system is the ability to both “fill” and “unfill”the fuel tank. The fuel dispensing hose (0708) may be configured tosupport dispensing of fuel from a fuel reservoir (0709) into (0711) thefuel tank (0707), so as to “fill” the fuel tank (0707) to thepredetermined “full” level (0713). This situation is the one commonlyoccurring when the customer returns a rental/lease vehicle with a fueltank that is not at the predetermined “full” level. The fuel dispensinghose (0708) fills the fuel tank (0707) to the predetermined “full” level(0713) as measured by the fuel level sensor system (0706) describedpreviously. The fuel dispensing hose (0708) generally receives fuel froma fuel reservoir/pump (0709) system under control of either the computersystem (0701) and/or the fuel level sensor electronics (0706). Inoptimal configurations, the control of the fuel reservoir/pump (0709)system is wireless.

In addition to guaranteeing a “full” tank upon restocking of therental/lease vehicle into inventory after return by the customer, thesystem as depicted may also remove fuel from the fuel tank (0707) via asuction siphoning tube associated with the fuel dispensing hose (0708)to permit recovery of fuel within the fuel tank that is above thenominal “full” fuel level (0713). This removal of fuel (0712) by thefuel dispensing hose enables recovery of excess fuel tank (0707)contents and storage of same within a fuel storage reservoir (0710) forapplication to other rental/lease vehicles (0714) (after appropriatefiltering if necessary). The removal of excess fuel above the “full”fuel level (0713) within the fuel tank (0707) ensures that fuel is notwasted by spillage from the fuel tank or other mechanisms of fuel lossassociated with “overfull” fuel tanks. This recovery of excess fuel tankstorage also improves the economy by eliminating excess evaporation offuel tank contents to the atmosphere.

As part of the fuel level sensor calibration procedure, the capabilityto remove fuel from the fuel tank also permits full calibration of thefuel level sensor by removing in some circumstances all of the fuel fromthe fuel tank, and then subsequently adding fuel at a known rate orincremental quantity and then calibrating the fuel level sensor at eachknown fuel tank storage level.

Several variants of this preferred embodiment are possible, includingscenarios wherein the computer system drives the transfer of fuel fromthe fuel dispenser (0708) to the fuel tank (0707). Fuel sensorcalibration data can be used by the computer system to determine fueltank levels, or this information can be incorporated into the fuel tanksensor itself to report actual fuel tank contents rather than simplyrecording ultrasonic return echo times. In some sophisticatedembodiments the raw data associated with the ultrasonic return echo maybe reported back to the computer system (0701) for analysis and accuratedetermination of the fuel tank contents. Multiple ultrasonicfrequencies, some including harmonics, may be utilized to provide a moreaccurate indicator of fuel tank contents in some circumstances.

Rental/Lease Fuel Management Method (0800)

The rental/lease fuel management system described above has anassociated method architecture as generally illustrated in FIG. 8(0800). The method steps generally comprise the following:

-   -   Calibrating the fuel tank level sensor to the specific fuel tank        on the rental/lease vehicle (0801);    -   Setting a “full” level for the fuel tank (0802);    -   Filling the fuel tank to the “full” level (0803);    -   Issuing the rental/lease vehicle to the customer (0804);    -   Returning the rental/lease vehicle from the customer (0805);    -   Accurately measuring the fuel level in the fuel tank (0806);    -   If the fuel tank is less than full, proceeding to step (9)        (0807);    -   Removing and/or storing sufficient fuel from the fuel tank to        return the fuel tank to a “full” fuel level and proceeding to        step (10) (0808);    -   Filling the fuel tank to a “full” fuel level and billing the        customer for fuel added to the fuel tank (0809);    -   Determining if there are other rental/lease customers to be        serviced by the rental/lease vehicle, and if so, proceeding to        step (4) (0810);    -   Terminating the rental/lease fuel management method (0811).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

It should be noted that the fuel tank level data (0410, 0610) generatedby this fuel tank calibration procedure generally includes paired datapoints including a known fuel tank level and the corresponding returnecho time. Given the nonlinear nature of the ultrasonic echo waveforms,this table may be highly nonlinear and in some circumstances require theuse of ultrasonic harmonics (added as a third vector in the calibrationtable) to accurately determine the fuel level within the fuel tank. Thecalculation of an accurate fuel tank level may require the use of anonlinear fitting function to be applied to the calibration data (0410,0610). Nonlinear interpolation utilizing calibration datasets such asthose illustrated in FIG. 4 (0410) and FIG. 6 (0610) are well known tothose skilled in the mathematical arts.

Fuel Tank Fuel Management Cycle Method (0900)

The present invention anticipates a wide variety of fuel managementcycles will be appropriate for use with the present invention inaddition to the ones previous described in FIG. 2 (0200), FIG. 4 (0400),FIG. 6 (0600), and FIG. 8 (0800). Several of these have application tovehicle rental/lease scenarios, and many will utilize elements of thepreviously described methods. One preferred fuel tank management cyclemethod is generally illustrated in FIG. 9 (0900) and comprises thefollowing steps:

-   -   Accurately determining the fuel tank level (0901);    -   Transmitting the fuel level sensor value via a transponder to a        fuel dispenser (0902);    -   Refilling the fuel tank using the fuel dispenser to a        predetermined “full” level (0903);    -   Logging the current fuel tank level value to a customer database        (0904);    -   Issuing the rental/lease vehicle to the customer (0905);    -   Receiving the returned rental/lease vehicle from the customer        into the rental/lease vehicle intake system (0906);    -   Accurately determining the fuel tank level in the rental/lease        vehicle (0907);    -   Transmitting the fuel level sensor value via transponder to the        fuel accounting system (0908);    -   Logging the current fuel tank level value to the customer        database (0909);    -   Subtracting the measured fuel tank fuel level from a        predetermined “full” fuel tank value to determine a “refill”        quantity (0910);    -   Dispensing fuel to the fuel tank based on the “refill” quantity        (0911);    -   Billing the rental/lease customer based on the “refill” fuel        quantity (0911).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

Ultrasonic Fuel Level Sensor (1000)

Many preferred exemplary embodiments of the present invention utilize anultrasonic fuel level sensor to accurately determine the fuel levelwithin the fuel tank. A system block diagram of the general architectureof one preferred exemplary embodiment of this sensor is illustrated inFIG. 10 (1000). This system utilizes an ultrasonic (typicallypiezoelectric) transducer (1001) with associated ultrasonic waveguide(1002) to focus ultrasonic energy/pulses (1003) for transmission (1004)into a fuel tank (1005). Return echo waveforms (1006) are returned forfocusing by an ultrasonic waveguide (1002) and detection by theultrasonic transducer (1001). Note this embodiment optimally utilizes asingle piezoelectric transducer (1001) and waveguide (1002) for thegeneration and detection of the ultrasonic waves. Other embodiments mayutilize separate transducers for generation and detection and/orseparate waveguides for channeling of the ultrasonic energy.

The gist of the system as depicted is to measure the fuel tank level byimpinging ultrasonic energy down the fuel tank filler tube and detectthe return time associated with the echoed ultrasonic wave. The shorterthe echo time, the fuller the tank level. Note also that due to thehighly nonlinear characteristics of the fuel tank resonance structures,the returned waveform may incorporate other characteristics other thanecho time that can be used to more accurately determine the fuel tanklevel. Therefore, in some circumstances a spectral analysis of thereturned echo may be necessary to more fully determine the fuel tanklevel by matching the returned echo to a known set of echo patternsstored in a calibration database.

To support the generation of the ultrasonic waveforms and the detectionof the return echo times, a control logic state machine (1007) operatesto gate excitation of the ultrasonic transducer (1001) via use of abridge driver (1008) that takes its stimulus from a clock gating circuit(1009). The clock gating circuit (1009) simply provides stimulus to thebridge driver (1008) in response to an oscillator (1010) and/or phaselocked loop (1011) that generates the desired ultrasonic transducer(1001) stimulus. Note that the control logic (1007) can operate tochange the characteristics of the phase locked loop (1011) and/or gatecontrol (1009) circuitry to modify the ultrasonic waveform used toaffect the fuel tank (1005) fuel level detection.

After the control logic/state machine (1007) initiates an ultrasonicwaveform or pulse to probe the fuel tank (1005), the bridge driver(1008) goes inactive, and a sensing amplifier (1012) utilizes theultrasonic transducer (1001) to sense the return echo from the fuel tank(1005). During this time a return echo time counter (1013) has beenactivated by the control logic/state machine (1007) to begin countingclock cycles from a clock generator (1014) and/or oscillator (1015). Theperiod of the clock generator (1014) and/or oscillator (1015) istypically very short in comparison to the ultrasonic source period topermit accurate determination of the return echo time. Once the returnecho is detected, the return echo time counter (1013) output is saved ina latch (1016) for use as the returned echo time (1017).

The returned echo time (1017) is then used within the fuel sensorcalibration table to determine the exact amount of fuel within the fueltank (1005) by interpolating between points of known fuel tank contentsand their associated return echo times that have been saved as a resultof a previous calibration procedure. The beauty in this approach is thata generic ultrasonic transducer (1001) can be utilized with a widevariety of fuel tanks (1005) and environments and be individuallycalibrated to the fuel tank such that variances in construction,components, etc. can be compensated for without any human intervention.For example, if in some preferred exemplary embodiments the ultrasonictransducer (1001) is incorporated into a fuel tank filler cap (“gascap”), a single physical embodiment of this filler cap may operate on awide variety of vehicles from a given manufacturer, even though the fueltanks and associated capacities of these tanks may vary widely withinthe range of models supplied by the vehicle manufacturer.

Referencing FIG. 10 (1000), an exemplary timing diagram (1020)associated with some preferred exemplary embodiments of the circuitryshown in FIG. 10 is illustrated. Generally speaking, the state machine(1007) is run by a sample clock (1021), off of which an ultrasonic wavetrigger (UWT) (1022) is generated. This UWT signal (1022) is used togate the bridge driver (1008) to generate an ultrasonic wave/pulse(1023) that is emitted by the ultrasonic transducer (1001) into the fueltank (1005). The return echo signal (1024) is then detected by theamplifier/detector (1012) to produce an echo detection signal (1025).This echo detection signal (1025) is used to terminate the counterenable (1026) for the return echo time counter (1013) that was countingtimer clocks (1027) during its enable period. The echo detection signal(1025) is also utilized to latch the return echo time counter (1013)value into the storage latch (1016) for use as the return echo timevalue (1017).

One skilled in the art will recognize that the circuitry depicted inFIG. 10 (1000) may be easily incorporated into one or more applicationspecific integrated circuits (ASICs) and/or incorporated within manyconventional integrated microcontrollers (with appropriate embeddedsoftware) and/or FPGAs. The present invention makes no limitation on theparticular hardware utilized to achieve the functionality associatedwith the ultrasonic fuel level sensor embodiments.

Ultrasonic Fuel Sensor Integrated Float Embodiment (11001

While the present invention can be embodied in many preferredembodiments, some of these preferred embodiments incorporate a fuel capfuel tank level sensor, and a subset of these preferred embodimentsutilize an ultrasonic fuel level sensor in this context. Within thissubset of preferred embodiments, FIG. 11 (1100) illustrates what isthought to be a best mode implementation of part of this fuel sensorarchitecture.

Referencing FIG. 11 (1100), the fuel cap (1101) incorporating theelectronics for the ultrasonic fuel sensor system is fixed to a fueltank (1102) by virtue of a fuel tank filling tube (1103). Connected tothe fuel cap (1101) is a sensor tube (1104) that extends from thefilling cap (1101) to the bottom (1105) of the fuel tank (1102). Thissensor tube (1104) permits ultrasonic waves/pulses (1106) to traverse(1107) the sensor tube (1104) until they impinge on a float ball (1108)at which point they are reflected (1109) back (1110) to the fuel cap(1101) for detection by the fuel level sensor electronics. The floatball (1108) position within the sensor tube (1104) is dictated by theprecise fuel level (1111) within the fuel tank (1102). The end of thesensor tube (1104) may be screened (1112) to ensure proper retention ofthe float ball (1108) within the sensor tube (1104). The float ball(1108) may be constructed of any material that has a specific gravityless than that of the fuel within the fuel tank (1102), but the bestknown mode for construction would utilize plastic, optimally with ahollow interior.

The sensor tube (1104) in this context permits fuel to be removed fromthe fuel tank (1102) during both fuel tank level sensor calibrationand/or fuel tank level standardization (removal of excess fuel tankfuel) upon return of rental/lease vehicles by the customer. A resealablefuel entrypoint (1113) at the distal end of the fuel cap (1101) permitsaccess to the sensor tube (1104) for this purpose. This resealable fuelentrypoint (1113) can take many forms, with plastic being the preferableconstruction material. Molded plastic caps, including variants of fueltank caps (as illustrated by example (1120) extracted from U.S. Pat. No.D294,820 (Mar. 22, 1988)), are well known in the art and thus one ofordinary skill in the art would be able to fabricate this in anysuitable form based on the context of application for the invention.

Note that while the sensor tube may be advantageously used with avariety of fuel level sensors, including ultrasonic embodiments, it isequally well adapted for use with situations in which existing fuel tankfuel level sensors are augmented with inline fuel level sensormeasurement subsystems as detailed in FIG. 12 (1200) and describe below.

Inline Fuel Level Sensor System Embodiment (1200)

While the present invention anticipates many forms of fuel level sensorimplementation, the preferred embodiments generally utilize ultrasonicfuel level sensing methodologies as detailed herein. However, in somecircumstances the present invention can be optimally implemented byeffectively utilizing the existing fuel level sensor that resides withinthe fuel tank of the vehicle. These fuel sensors generally comprise aresistor/potentiometer whose resistance varies based on the fuel levelwithin the fuel tank. As generally illustrated in FIG. 12 (1200), inthese configurations the fuel tank (1201) typically incorporates a fuelgauge sensor (1202) that produces a voltage (or equivalently aresistance) based on the level of fuel within the fuel tank (1201). Thisfuel level sensor (1202) is generally connected to a vehicle fuel gauge(1203) (or an electronic equivalent) via a cable harness withappropriate electrical connectors. Note that in some embodiments thefuel gauge sensor (1202) may take the form of some other type of sensor(pressure, etc.) that describes the level of fuel within a fuel tanksystem, and thus the illustration of the fuel gauge sensor (1202) shouldbe given its broadest possible interpretation in this context.

The present invention in some preferred embodiments can utilize thissensor with a high level of accuracy to determine the exact level offuel within the fuel tank (1201). To implement this system a signaltapping cable harness (1210) is inserted into the normal connector flowbetween the fuel gauge sensor (1202) and the vehicle fuel gauge (1203).This jumper harness permits the signal levels emitted by the fuel gaugesensor (1202) to be intercepted by an analog-to-digital (A/D) converter(1211) that is part of the fuel management system. The digitized datafrom the A/D converter (1211) is fed into the fuel level sensortransponder (1212) for wireless transmission to the fuel accountingsystem as previously described.

Within the context of the inline fuel level sensor retrofit there existsthe option of incorporating parasitic power operation of the fuel sensorelement to eliminate the need for internal batteries or external powersupply support. This may be accomplished by utilizing a diode (1214) toparasitically charge a capacitor (1215) using a small portion of thecurrent that would normally flow through the fuel tank fuel sensorpotentiometer (1202). This small current requirement is then held inreserve (as Vcc internal power (1217)) for the electronics of the fuellevel sensor measurement subsystem (1210) to operate the A/D converter(1211) and associated wireless transponder (1212). In some preferredembodiments, the diode (1214) and capacitor (1215) may be replaced by aDC-to-DC boost converter (1216) to enable functioning of the system overa wide range of operating fuel sensor voltages. DC-to-DC boostconverters are well known in the art and one skilled in the art willhave a number of possible selections for this function block that arewell documented in the prior art.

The advantage to this parasitic power operation is that the fuel levelsensor measurement subsystem (1210) can be installed proximal to thefuel tank and wirelessly interrogated as part of the overall fuelmanagement system without the need for complex and costly retrofittingof any vehicle system or component. It is anticipated the optimalmethodology to implement this wireless communication link is detailedwithin (and hereby incorporated by reference) U.S. Pat. No. 5,025,486(now expired) for WIRELESS COMMUNICATION SYSTEM WITH PARALLEL POLLING,issued on Jun. 18, 1991, to Kevin M. Klughart. Within this context it isenvisioned that a wireless UHF transmitter would in many preferredembodiments be an optimal methodology of implementing the transponderlink from the fuel level sensor to the fuel accounting system.

As with the ultrasonic fuel level sensors previously discussed, the fuelgauge sensor (1202) in this case can be calibrated by evacuating thefuel tank and then filling the fuel tank with known quantities of fueland then accurately recording the fuel gauge sensor (1202) output withthe A/D converter (1211) and creating a calibration table for the fueltank (1201)/fuel sensor (1202) combination. The use of individualcalibration for each fuel tank (1201)/fuel sensor (1202) combinationensures highly accurate measurement of fuel tank (1201) fuel levels,even if the fuel gauge sensor (1202) is nonlinear, the fuel tank (1201)is irregularly shaped, or other environmental factors such as variancesin fuel gauge sensor characteristics make it impossible to utilizestandardized conversion tables to directly read the output of the fuelgauge sensor (1202).

As discussed elsewhere in this document, the use of a temperature sensor(1213) in conjunction with the fuel level sensor may be advantageouslyused in some preferred embodiments to compensate for fuel expansion indetermining the actual fuel level within the fuel tank standardized to aknown volumetric level and temperature.

Inline Fuel Level Sensor Calibration Method (1300)

The inline fuel level sensor system described above has an associatedmethod architecture as generally illustrated in FIG. 13 (1300). Themethod steps generally comprise the following:

-   -   Draining the fuel tank to a known level (1301);    -   Initializing the fuel level sensor calibration state to indicate        that the sensor is being calibrated to the fuel tank (1302);    -   Triggering a fuel dispenser to transfer a known quantity of fuel        into the fuel tank (1303);    -   Sensing the fuel level sensor voltage using an analog-to-digital        converter (1304);    -   Recording the measured fuel level sensor voltage and fuel tank        level in a fuel tank calibration database table (1310) for use        later in determining the fuel level within the fuel tank (1305);    -   Determining if the fuel tank fill level has been reached, and if        not, proceeding to step (3) (1305).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

It should be noted that the fuel tank level data (1310) generated bythis fuel tank calibration procedure generally includes paired datapoints including a known fuel tank level and the corresponding measuredsensor voltage. Given the nonlinear nature of the fuel sensor voltage,this table may be highly nonlinear. The calculation of an accurate fueltank level may require the use of a nonlinear fitting function to beapplied to the calibration data (1310). Nonlinear interpolationutilizing calibration datasets such as those illustrated in FIG. 13(1310) are well known to those skilled in the mathematical arts.

While the source of calibration data may differ between the use ofultrasonic fuel level sensors and the analog fuel level sensors presentin many vehicle fuel tanks, the overall calibration procedures withrespect to the present invention system/method are the same, and providesufficient accuracy, precision, and repeatability to ensure thataccurate and precise fuel level measurements can be made to support theremaining aspects of the fuel management system/method described herein.

Low/Zero Power Fuel Sensor Embodiment (1400)

While the present invention may utilize a wide variety of fuel levelsensors within the context of the disclosed fuel managementsystem/method, one preferred exemplary embodiment of the fuel levelsensor utilizes a design structure that is “zero” or near “zero” power,and in many cases can be fabricated without the use of an internal orexternal power supply by using parasitic power extraction techniques.Many of the wireless techniques that utilize an inductive pickup coilthat is shunted with a diode or other switching element (typicallyutilized in product anti-theft systems and the like) are discussed (andreferenced in patents cited therein, many of which are expired) withinU.S. Pat. No. 7,113,094 for APPLICATION FOR RADIO FREQUENCYIDENTIFICATION SYSTEMS, issued on Sep. 26, 2006 to Sharon R. Garber, et.al, all of which is incorporated herein by reference.

The general structure of this particular low/zero power preferred fuellevel sensor embodiment is illustrated in FIG. 14 (1400). The generalarchitecture of this fuel level sensor makes use of inductive and/or RFtransmission (1411, 1421) from a power transmitter (1410) (typicallyintegrated or attached to a portable data entry device (1412)) to apower receiver (1420) (under control of a state machine (1430)) thatcommunicates with the fuel level sensor measurement subsystem (1440).The combination of a power receiver (1420) and appropriate powertransfer circuitry in conjunction with appropriate state machinecircuitry (1430) permits the fuel level sensor subsystem (1440) tooperate in some preferred embodiments without any embedded power sourcesuch as a battery or the use of wiring to the vehicle electrical system.Shunting of the power receiver (1420) inductive pickup can be sensed bythe power transmitter (1410) to affect data transmission from thereceiver (1420) to the transmitter (1410) in some circumstances.

Referencing FIG. 14 (1400), the power receiver subsystem (1420) istypically embodied wherein an inductive pickup (1421) is routed througha configuration matrix (1422) (typically under control of a statemachine (1430)) to service an element within a power load matrix (1423).This power matrix load (1423) may also generate appropriate control/datasignals (1424) to operate the remainder of the fuel level sensormeasurement subsystem (1440). Depending on the state (1430) of theconfiguration matrix (1422), a different element within the power loadmatrix (1423) is selected for connection to the inductive pickup (1421),resulting in a different functional relationship between the powertransmitter (1410) and the fuel level sensor measurement subsystem(1440).

The present invention anticipates a wide variety of methodologies thatmay be used to implement the configuration matrix (1422). However, theuse of solid state switches such as MOSFETs, BJTs, IGBTs, SCRs, and/orTRIACs are thought to be optimal selections for this implementation. Thespecific elements contained within the power load matrix (1423) may varywidely, but optimal selections for these elements are generally thoughtto comprise those illustrated in FIG. 15 (1500).

Power Receiver Configuration Switching States (1500)

The switching states associated with power receiver configuration blockdiagram illustrated in FIG. 14 (1400) may take many forms, but it isthought that the scenarios depicted in FIG. 15 (1500) are optimal. Inthese examples, the configuration matrix (1422) has been symbolicallyidentified by a configuration matrix boundary (1501) to separate theinductor pickup (1421) from the power load matrix elements (1423).

It should be noted that in many preferred embodiments the fuel levelsensor measurement subsystem will utilize a low power clock oscillatorin conjunction with state machine operations and other functions. Thepresent invention specifically anticipates (and incorporates herein byreference) the utilization of the low power crystal oscillatortechnologies detailed in U.S. Pat. No. 5,546,055 for CRYSTAL OSCILLATORBIAS STABILIZER, issued on Aug. 13, 1996 to Kevin M. Klughart. Theavailability of a low power clock oscillator source as depicted in thisdocument permits definition and detection of distinct periods of idleand/or waveform activity in the inductive pickup and may aid information of the state machine controller as generally depicted in FIG.14 (1430).

Note when interpreting the symbolic state functions in FIG. 15 (1500)that various time periods, idle times, and detected clock counts may bereferenced to an internal clock generated within the fuel level sensormeasurement system or in some circumstances referenced to detectedpulses induced within the inductive pickup by the remote transmitter.

Power Charge State (1510)

The power charge state connects the inductor pickup to a bridgerectifier or other current rectification switch to charge a capacitorthat supplies Vcc operating voltage for the remainder of the fuel levelsensor measurement subsystem. Generally speaking, the default operatingmode of the system is this state, in that extraneous electromagneticenergy impinging the inductive pickup will be converted into availableenergy to support the low-power requirements of the fuel level sensormeasurement system.

As part of this state, the generation of a VccOK signal indicating thatthe supply voltage has reached an acceptable operating point isanticipated to be part of this process. The Vref reference leveldefining this operating point can be derived from stacks of chained VGSsubthreshold MOSFET devices or other techniques well known in the art.

Reset State (1520)

The RESET state is entered by inspecting the inductive pickup (typicallyusing a comparator, optimally incorporating hysteresis) to determineincident received waveforms. If, after an appropriate idle delay, apredetermined RESET count of pulses is detected, the RESET state isactivated. This RESET state puts the remainder of the system in a statesuitable to receive commands via the inductive pickup from the remotewireless device.

Write 0 State (1530)

The WRITE 0 state is entered by inspecting the inductive pickup(typically using a comparator, optimally incorporating hysteresis) todetermine incident received waveforms. If, after an appropriate idledelay, a predetermined WRITE 0 count of pulses is detected, the WRITE 0state is activated. This state transfers a logic 0 as a write datastream to the fuel level sensor measurement subsystem.

Write 1 State (1540)

The WRITE 1 state is entered by inspecting the inductive pickup(typically using a comparator, optimally incorporating hysteresis) todetermine incident received waveforms. If, after an appropriate idledelay, a predetermined WRITE 1 count of pulses is detected, the WRITE 1state is activated. This state transfers a logic 1 as a write datastream to the fuel level sensor measurement subsystem.

Read 0 State (1550)

The READ 0 state is entered by inspecting the inductive pickup(typically using a comparator, optimally incorporating hysteresis) todetermine incident received waveforms. If, after an appropriate idledelay, a data 0 is to be read (transmitted) the inductive pickup isshorted (typically through a diode) for a predetermined READ 0 count ofpulses detected from the inductive pickup. This state transfers logic 0as a read data stream from the fuel level sensor measurement subsystem.The orientation of the diode in this configuration may be dependent onthe type of data to be transmitted back to the originating transmitter(including the type of detector utilized in the originatingtransmitter), and is not necessarily as shown in the diagram.

Read 1 State (1560)

The READ 1 state is entered by inspecting the inductive pickup(typically using a comparator, optimally incorporating hysteresis) todetermine incident received waveforms. If, after an appropriate idledelay, a data 1 is to be read (transmitted) the inductive pickup isshorted (typically through a diode) for a predetermined READ 1 count ofpulses detected from the inductive pickup. This state transfers logic 1as a read data stream from the fuel level sensor measurement subsystem.The orientation of the diode in this configuration may be dependent onthe type of data to be transmitted back to the originating transmitter(including the type of detector utilized in the originatingtransmitter), and is not necessarily as shown in the diagram.

Ultrasonic Write/Read State (1570)

The ultrasonic write/read state is configured by connecting theinductive pickup to the ultrasonic transducer associated with the fuellevel sensor subsystem. This connection permits incident wireless energyto be transmitted directly from the inductive pickup to stimulate theultrasonic transducer to produce the ultrasonic wave/pulse necessary tomeasure the fuel level within the fuel tank (assuming an ultrasonic fuellevel measurement embodiment). The return ultrasonic echo can be eitherdecoded by logic within the fuel level sensor measurement system or insome instances transmitted directly back via the inductive pickup to theoriginating transmitter for determination of the return echo time.

Fuel Management Volume Standardization Method (1600)

An overarching goal of the fuel management system/method describedherein is volumetric standardization of fuel within a fuel tank, suchthat discrepancies between “full” fuel tanks on rental/lease vehicles tocustomers are accounted for when the rental/lease vehicle is returned bythe customer. One issue not addressed by the prior art is the volumetricdifferential in fuel that is due to thermal expansion/contraction of thefuel itself within the fuel tank. As a result of this thermalexpansion/contraction, there are many instances in which vehiclerental/lease firms “overfill” their fleet of returned vehicles due todifferentials in the temperature of their fuel storage versus theambient temperature of the vehicle fuel tank.

As an example, the following fuels and their volumetric coefficientthermal expansion are listed:

Volumetric Coefficient of Thermal Expansion Fuel 10⁻⁶/° C. Diesel 828Ethanol 750 Gasoline 950The coefficient of volumetric expansion values can have a significantimpact on the measurement of fuel within the fuel tank. For example a 20gallon gasoline filled fuel tank experiencing a temperature differentialof 25 degrees Celsius will incur a volumetric differential ofapproximately half a gallon of fuel. This means that if the fuel isdispensed from a (typically cooler) underground storage tank and placedwithin a warmer fuel tank, the fuel will expand due to the increasedtemperature and be volumetrically larger than the amount of fueldispensed from the fuel pump.

One preferred embodiment of the present invention coordinates thefilling of the fuel tank with knowledge of the temperature of the fuelwithin the fuel dispensing storage reservoir to ensure that once thefuel is loaded into the fuel tank, its expansion due to the differentialin ambient temperature and that of the fuel dispensing storage reservoirwill produce a fuel tank level that meets the predetermined “full” fueltank specification. In this manner, the fuel tank will not become“overfull” by the addition of fuel that would eventually expand due toincreased temperature and result in fuel spillage and waste.

This approach to fuel management, incorporating fuel temperature as wellas volume in the dispensing of fuel to the fuel tank, may be augmentedin some preferred embodiments to normalize the amount of fuel residentin the tank to a known temperature standard. For example, it might bepossible to define a nominal 20 gallon capacity fuel tank as “full” ifit contains 18 gallons of fuel at 25 degrees Celsius. Thus, filling thefuel tank would necessarily require interrogation of the temperature ofthe fuel storage reservoir used by the fuel dispenser and the ambienttemperature of the fuel within the fuel tank. In this fashion, the fuelmanagement system can manage the energy content transferred to each fueltank during the refill cycle to ensure that each “full” fuel tankcontains a specified energy content based on normalized fuel volume at astandardized temperature.

The fuel management volume standardization system described above has anassociated method architecture as generally illustrated in FIG. 16(1600). The method steps generally comprise the following:

-   -   Setting the standard for fuel tank capacity based on fuel volume        and standard (nominal) volumetric temperature (1601);    -   Issuing the rental/lease vehicle to the customer (1602);    -   Returning the rental/lease vehicle from the customer (1603);    -   Measuring the fuel source and fuel tank temperatures (1604);    -   Sensing the fuel tank level and converting this fuel level to a        standard volume at nominal temperature (1605);    -   If the fuel tank is less than the standardized “full” level,        proceeding to step (8) (1606);    -   Removing/storing fuel from the fuel tank to return the fuel tank        to the nominal “full” level at the given fuel tank temperature,        then proceeding to step (11) (1607);    -   Calculating the needed fuel amount from the fuel source to        “fill” the fuel tank to the nominal “full” level at the fuel        tank temperature (1608);    -   Transferring the calculated fuel amount from the fuel source to        the fuel tank with an automated fuel dispenser (1609);    -   Billing the customer for fuel added to the fuel tank (1610);    -   Determining if there are other rental/lease customers to be        serviced by the rental/lease vehicle, and if so, proceeding to        step (2) (1611);    -   Terminating the fuel management volume standardization method        (1612).

One skilled in the art will recognize that these method steps may beaugmented or rearranged without limiting the teachings of the presentinvention.

System Summary

The present invention system anticipates a wide variety of variations inthe basic theme of construction, but can be generalized as a fuelmanagement system comprising:

-   -   (a) fuel level sensor;    -   (b) fuel level sensor transponder; and    -   (c) fuel accounting system;    -   wherein    -   the fuel level sensor determines the current fuel contents of a        fuel tank and produces a measurement output responsive to the        contents;    -   the fuel level sensor transponder accepts the measurement output        and transmits the measurement output to the fuel accounting        system;    -   the fuel accounting system saves as a stored data records the        transmitted measurement output into a database associated with        the fuel consuming system associated with the fuel tank; and    -   the fuel accounting system determines fuel consumption of the        fuel consuming system by noting the differential between the        stored data records within the database.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Method Summary

The present invention method anticipates a wide variety of variations inthe basic theme of implementation, but can be generalized as a fuelmanagement method wherein the method comprises:

-   -   (1) Accurately sensing the level of fuel in a fuel tank using a        fuel level sensor having a fuel level sensor measurement output;    -   (2) Transmitting the fuel level sensor measurement output via a        fuel level sensor transponder;    -   (3) Receiving the transmitted fuel level sensor measurement        output as current fuel level information in a fuel accounting        system;    -   (4) Tracking the fuel level information associated with a given        customer or vehicle in a customer database;    -   (5) Determining if fuel tank refilling is enabled, and if not,        proceeding to step (8);    -   (6) Subtracting the sensed fuel level from a “full” tank value        to determine a fuel tank “refill” quantity;    -   (7) Refilling the fuel tank using a fuel dispenser system that        is controlled by the fuel accounting system based on the        difference between the sensed fuel tank level and a        predetermined “full” fuel tank level; and    -   (8) Terminating the fuel accounting cycle.

This general method summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

System/Method Variations

The present invention anticipates a wide variety of variations in thebasic theme of construction. The examples presented previously do notrepresent the entire scope of possible usages. They are meant to cite afew of the almost limitless possibilities.

This basic system and its associated method may be augmented with avariety of ancillary embodiments, including but not limited to:

-   -   An embodiment wherein the fuel level sensor further comprises a        fuel tank cap utilizing an ultrasonic transducer to determine        the current fuel contents by transmitting ultrasonic energy into        the fuel filler tube of the fuel tank and measuring the return        echo time of the ultrasonic energy after the ultrasonic energy        impinges on the current fuel contents.    -   An embodiment wherein the fuel tank cap further comprises a fuel        sensor tube fitting within the filler tube of the fuel tank, the        fuel sensor tube further comprising a float ball positioned to        float on the surface of fuel contained within the fuel tank.    -   An embodiment wherein the fuel accounting system further        comprises a fuel dispensing apparatus that dispenses fuel to the        fuel tank based on the differential between a predetermined        “full” fuel tank level and the current fuel contents.    -   An embodiment wherein the fuel accounting system further        comprises a fuel dispensing apparatus that (a) dispenses fuel to        the fuel tank based on the differential between a predetermined        “full” fuel tank level and the current fuel contents if the fuel        tank fuel level is below a predetermined “full” level, or (b)        removes fuel from the fuel tank based on the differential        between a predetermined “full” fuel level and the current fuel        contents if the fuel tank fuel level is above a predetermined        “full” level.    -   An embodiment wherein the “full” fuel tank level and the        measurement of the current fuel contents are temperature        standardized based on the respective temperature of fuel within        the fuel tank and the temperature of fuel supplied by the fuel        dispensing apparatus.    -   An embodiment wherein the fuel level sensor measurement output        is compensated based on the characteristics of the fuel tank and        the fuel level sensor by interpolating values contained in a        fuel tank calibration table, the fuel tank calibration table        being generated by a process of evacuating the contents of the        fuel tank followed by incremental additions of fuel to the fuel        tank coupled with recording the fuel level sensor measurement        output associated with the fuel level corresponding to the        incremental fuel additions.    -   An embodiment wherein the fuel level sensor transponder        communicates with the fuel accounting system utilizing wireless        low/zero power communication system, the communication system        further comprising a power transmitter controlled by the        accounting system, and a power receiver configuration switch and        power reception state machine interfaced to and controlled by        the fuel level sensor.    -   An embodiment wherein the power receiver configuration switch        further comprises an inductive pickup electrically connected to        a configuration matrix that is electrically connected to        elements of a power load matrix.    -   An embodiment wherein the fuel level sensor further comprises an        A/D converter, the A/D converter further comprising an analog        input and digital output, the analog input connected to an        inline fuel level sensor integrated into the fuel tank and the        digital output connected to the fuel level sensor transponder.    -   An embodiment wherein the fuel management system/method is        integrated into a vehicle rental/lease accounting system/method.    -   An embodiment wherein the fuel level sensor is embodied in a        fuel tank cap incorporating a display, with the fuel cap display        triggered via a magnetic Hall effect sensor. This variant may        incorporate a magnetic source in the vehicle body covering of        the fuel tank cap to affect this display triggering.    -   An embodiment wherein the fuel level sensor is embodied in a        fuel tank cap incorporating a visual indicator that indicates if        the fuel tank is “full” and/or the current fuel level within the        fuel tank.    -   An embodiment wherein the fuel level sensor is embodied in a        fuel tank cap incorporating a pushbutton switch to trigger a        visual indicator that indicates if the fuel tank is “full”        and/or the current fuel level within the fuel tank.    -   An embodiment wherein the fuel level sensor is embodied in a        fuel tank cap incorporating a periodic trigger to display a        visual indicator that indicates if the fuel tank is “full”        and/or the current fuel level within the fuel tank.    -   An embodiment wherein the fuel level sensor is embodied in a        fuel tank cap incorporating a visual display to indicate whether        the fuel tank is “unfull”, “full”, or “overfull”.

One skilled in the art will recognize that other embodiments arepossible based on combinations of elements taught within the aboveinvention description.

CONCLUSION

A fuel management system and method that permits accurate accounting offuel consumption within the context of a fuel consuming system has beendisclosed. The system/method may be broadly described as comprising afuel level sensor, fuel level sensor transponder, fuel accountingsystem, and optional regulated fuel dispenser. The fuel level sensoraccurately determines the contents of a fuel tank. This information isreported via fuel sensor transponder to a fuel accounting system thattracks the fuel consumption of the fuel consuming system and providesbilling information based on the detected fuel consumption. Thisaccounting information may be utilized within an optional regulated fueldispenser to refill the fuel tank to an accurately predetermined fuellevel for the next fuel management accounting cycle. While the presentinvention has many applications, one preferred embodiment targets fuelmanagement within the context of rental/lease vehicles and the like.

What is claimed is:
 1. A fuel management system comprising: a fuel level sensor which determines a current fuel level of a fuel tank and produces a measurement output responsive to said current fuel level, wherein said fuel level sensor is a fuel tank cap utilizing an ultrasonic transducer which transmits ultrasonic energy into a fuel filler tube of said fuel tank and measures the return echo time of said ultrasonic energy after said ultrasonic energy impinges on a surface of fuel contained within the fuel tank; a fuel level sensor transponder which accepts said measurement output responsive to said current fuel level and transmits said measurement output; a fuel accounting system which receives said transmitted measurement output, stores said transmitted measurement output into a database associated with a fuel consuming system of said fuel tank and calculates a difference between a predetermined fuel tank level and said current fuel level; and a fuel dispensing apparatus which dispenses fuel to said fuel tank based on said calculated difference if said current fuel level is below said predetermined level, wherein said predetermined fuel level and said current fuel level are temperature standardized based on respectively a first temperature of fuel within said fuel tank and a second temperature of fuel supplied by said fuel dispensing apparatus in order to ensure that when dispensing the calculated difference of fuel into the fuel tank, expansion due to a difference in the first temperature and the second temperature will produce a fuel level at said predetermined fuel tank level, and wherein said fuel level sensor measurement output is compensated based on characteristics of said fuel tank and said fuel level sensor by interpolating values contained in a fuel tank calibration table, said fuel tank calibration table being previously generated by a process of evacuating the contents of said fuel tank followed by incremental additions of fuel to said fuel tank coupled with recording said fuel level sensor measurement output associated with the fuel level corresponding to said incremental fuel additions.
 2. The fuel management system of claim 1 wherein said fuel tank cap further comprises a fuel sensor tube fitting within the fuel filler tube of said fuel tank, said fuel sensor tube fitting further comprising a float ball positioned to float on the surface of fuel contained within said fuel tank.
 3. The fuel management system of claim 1 wherein said fuel dispensing apparatus removes fuel from said fuel tank based on said calculated difference if said current fuel level is above said predetermined level.
 4. The fuel management system of claim 1 wherein said fuel level sensor transponder communicates with said fuel accounting system utilizing wireless low/zero power communication system, said communication system further comprising a power transmitter controlled by said accounting system, and a power receiver configuration switch and power reception state machine interfaced to and controlled by said fuel level sensor.
 5. The fuel management system of claim 4 wherein said power receiver configuration switch further comprises an inductive pickup electrically connected to a configuration matrix that is electrically connected to elements of a power load matrix.
 6. The fuel management system of claim 1 wherein said fuel level sensor further comprises an A/D converter, said A/D converter further comprising an analog input and digital output, said analog input connected to an inline fuel level sensor integrated into said fuel tank and said digital output connected to said fuel level sensor transponder.
 7. A fuel management method comprising: utilizing a fuel tank cap acting as a fuel level sensor which contains an ultrasonic transducer which transmits ultrasonic energy into a fuel filler tube of a fuel tank and measures a return echo time of said ultrasonic energy after said ultrasonic energy impinges on a surface of fuel contained within the fuel tank; transmitting said measured return echo time using a fuel level sensor transponder; receiving said transmitted measured return echo time in a fuel accounting system; determining a current fuel level based on said transmitted measured return echo time compared to characteristics of said fuel tank and said fuel level sensor by interpolating values contained in a fuel tank calibration table, said fuel tank calibration table being previously generated by a process of evacuating the contents of said fuel tank followed by adding incremental additions of fuel to said fuel tank coupled with recording a return echo time associated with the fuel level corresponding to each added incremental addition of fuel; storing in a database associated with a fuel consuming system of said fuel tank within the fuel accounting system said current fuel level; calculating a difference between a predetermined fuel tank level and said current fuel level; adjusting said calculated difference based on a first temperature of fuel within said fuel tank and a second temperature of fuel in a fuel dispensing apparatus in order to ensure that when dispensing the calculated difference of fuel into the fuel tank, expansion due to a difference in the first temperature and the second temperature will produce a fuel level at said predetermined fuel tank level; and dispensing fuel using said fuel dispensing apparatus to said fuel tank based on said adjusted calculated difference if said current fuel level is below said predetermined level.
 8. The fuel management method of claim 7 wherein said fuel tank cap further comprises a fuel sensor tube fitting within the fuel filler tube of said fuel tank, said fuel sensor tube fitting further comprising a float ball positioned to float on the surface of fuel contained within said fuel tank.
 9. The fuel management method of claim 7 wherein said fuel dispensing apparatus removes fuel from said fuel tank based on said adjusted calculated difference if said current fuel level is above said predetermined level.
 10. The fuel management method of claim 7 wherein said fuel level sensor transponder communicates with said fuel accounting system utilizing wireless low/zero power communication system, said communication system further comprising a power transmitter controlled by said accounting system, and a power receiver configuration switch and power reception state machine interfaced to and controlled by said fuel level sensor.
 11. The fuel management method of claim 10 wherein said power receiver configuration switch further comprises an inductive pickup electrically connected to a configuration matrix that is electrically connected to elements of a power load matrix.
 12. The fuel management method of claim 7 wherein said fuel level sensor further comprises an A/D converter, said A/D converter further comprising an analog input and digital output, said analog input connected to an inline fuel level sensor integrated into said fuel tank and said digital output connected to said fuel level sensor transponder.
 13. The fuel management method of claim 7 further comprising: determining if fuel tank refilling is enabled before calculating the difference between the predetermined fuel tank level and said current fuel level; terminating a fuel accounting cycle by not dispensing fuel from said fuel tank if the fuel tank refilling is not enabled; and proceeding with dispensing fuel from said fuel tank if the fuel tank refilling is enabled. 